Circuit Arrangement for Processing a Radio-Frequency Signal

ABSTRACT

Described herein is a circuit arrangement for processing a radio-frequency signal.

BACKGROUND

In a mobile terminal having a circuit arrangement, different operatingvoltages are often used in the circuit arrangement. A main supplyvoltage source, for example in the form of a battery or a rechargeablebattery, which is coupled to the circuit arrangement is usuallyavailable. This applies not only to mobile radio telephones but also,for example, to portable computers such as laptops, so-called personaldigital assistants (PDA), mobile music players, for example MP3 players,etc.

The power reserve of the mobile terminal is, as a rule, a limitedresource. Therefore, it is necessary for the circuit arrangement to beas efficient as possible. In order to ensure efficiency, a switchingconverter, for example a DC/DC converter, for converting the main supplyvoltage into the different operating voltages is often used to providethe different operating voltages. Switching frequencies of a few kHz tothe MHz range for driving the switching converter are selected dependingon the design of the switching converter. The problem of switchingfrequency components and/or their harmonics occurring, as interferencesignals, in a useful frequency range of the circuit arrangement or in aspecially protected system frequency range therefore arises.

SUMMARY

The present disclosure may be related to providing a circuit arrangementin which interference at a useful frequency of the circuit arrangement,which is caused by the switching frequency, is reduced as far aspossible.

The circuit arrangement for processing a radio-frequency signal has asignal processing region which can be supplied with a supply voltage anda frequency signal at a useful frequency. A voltage regulating unitwhich is intended to provide the supply voltage and can be supplied witha switching signal at a switching frequency is coupled to the signalprocessing region. A frequency signal supply means which is intended tosupply the frequency signal is also coupled to the signal processingregion. The frequency signal supply means is coupled, via a divider, tothe voltage regulating unit for supplying the switching signal, with theresult that the useful frequency is a multiple of the switchingfrequency.

The switching frequency is thus divided into a subharmonic of the usefulfrequency, as a result of which the harmonics generated by operation ofa voltage regulating unit fall to the useful signal and its harmonic.There is no interference close to the carrier, with the result thatcrosstalk of the switching signal to the useful frequency is reduced asfar as possible. In clear terms, deriving the switching frequency fromthe useful frequency using a divider inherently results in the harmonicsof the interference produced by operation of the voltage regulating unitbeing synchronized with the useful signal or in a distance between theuseful frequency and the interference frequency, which distance isdefined by a division factor, the division factor being able to beselected according to the system requirement. The division factor may bean integer or a rational number. Interference, which is caused byoperation of the voltage regulating unit, with the signal processing inthe signal processing region is thus reduced.

In one development according to the present disclosure, the signalprocessing region has a useful signal input for supplying a usefulsignal. The signal processing region comprises a modulator formodulating the useful signal onto the frequency signal. The signalprocessing region thus essentially ensures signal processing which isdetermined by the frequency signal. The useful frequency of thefrequency signal is thus a characteristic variable for signal processingin the signal processing region. One possible example of such a signalprocessing region is a radio-frequency modulator, for example for atransmitter of a communication system.

In one development according to the present disclosure, the signalprocessing region has a received signal input for receiving a receivedsignal. The signal processing region comprises a demodulator fordemodulating the received signal from the useful frequency to baseband.One example of such a signal processing region is a radio-frequencydemodulator application in a receiver circuit of a communication system.

In one implementation, the signal processing region has a poweramplifier.

In one implementation of the present circuit arrangement, the voltageregulating unit comprises a switching regulator. As a result of the useof a switching regulator, the voltage regulating unit has anenergy-efficient design.

In another implementation, the voltage regulating unit has a controlunit for controlling the switching signal. The control unit can be used,for example, to suppress individual pulses of the switching signal.Stable provision of the supply voltage by the voltage regulating unitcan be ensured using the control unit.

In one development of the circuit arrangement, the divider has anadjustable division ratio. It is thus possible to generate a variableswitching frequency. Use of a variable switching frequency makes itpossible to place the interference signals produced by the switchingoperations into a frequency range of the signal processing region insuch a manner that system requirements can be complied with. This isadvantageous, in particular, if the signal processing region is atransmitting or receiving unit.

In one implementation of the circuit arrangement, the latter has afrequency signal generator which is coupled to the frequency signalsupply means. The frequency signal is thus already provided in thecircuit arrangement, with the result that interference caused byexternal signals is reduced as far as possible.

In one development, the circuit arrangement has a second frequencysignal supply means for supplying a second frequency signal. In thiscase, the second frequency signal, for example, may likewise be suppliedto the signal processing region, with the result that two characteristicfrequencies may be present in the signal processing region. In thiscase, provision may be made of a switching element whose input can beconnected to the frequency signal supply means or to the secondfrequency signal supply means and whose output is coupled to the voltageregulating unit. As a result, the switching frequency can be derivedfrom the first or the second frequency signal in a corresponding manner.The corresponding waveform is influenced by a switching state of theswitching element.

In one implementation, the circuit arrangement is arranged in a mobileterminal. In this case, the circuit arrangement may be arranged, inparticular, in a transmitter or a receiver of a communication system.

BRIEF DESCRIPTION OF THE DRAWINGS

The detailed description is described with reference to the accompanyingfigures. In the figures, the left-most digit(s) of a reference numberidentifies the figure in which the reference number first appears. Thesame or similar numbers may be used throughout the drawings to referencelike features and components.

The disclosure is set forth in more detail below using a plurality ofexemplary implementations and with reference to the drawings, in which:

FIG. 1 shows a schematic illustration of one implementation of thecircuit arrangement according to the present disclosure;

FIG. 2 shows a schematic illustration of another implementation of thecircuit arrangement according to the present disclosure;

FIG. 3 shows a schematic illustration of a section of one implementationof the circuit arrangement according to the present disclosure;

FIG. 4 shows a schematic illustration of a section of one implementationof the circuit arrangement according to the present disclosure;

FIG. 5 shows a schematic illustration of a transceiver implementation ofthe circuit arrangement according to the present disclosure; and

FIG. 6 shows a schematic illustration of a power amplifierimplementation of the circuit arrangement according to the presentdisclosure.

DETAILED DESCRIPTION

FIG. 1 shows a schematic illustration of one implementation of thecircuit arrangement according to the present disclosure. The circuitarrangement has a signal processing region 100 which is coupled to aninput 101 for supplying a useful signal. The signal processing region100 processes the useful signal provided and uses it to generate anoutput signal which it provides for further signal processing or forreading out. For this purpose, the signal processing region 100 iscoupled to an output 102 for providing the output signal.

Furthermore, the signal processing region 100 is coupled to a frequencysignal supply means 103 which is used to provide the signal processingregion 100 with a frequency signal at a useful frequency. The frequencysignal is required for signal processing in the signal processing region100. For example, the signal processing region 100 may have ademodulator or a modulator for demodulating or modulating the usefulsignal onto the frequency signal. It is also conceivable for the signalprocessing region 100 to have combinational logic and for the frequencysignal to be a clock signal in the signal processing region 100.

The signal processing region 100 is supplied with power for signalprocessing using a supply voltage. This is effected using a supplyvoltage line 104 which is coupled to the signal processing region 100.The supply voltage line 104 connects the signal processing region 100 toa voltage regulating unit 105. The voltage regulating unit 105 providesthe supply voltage.

In the event of the circuit arrangement being arranged in an integratedsemiconductor component, the supply voltage is usually between 1 voltand 3 volts. The voltage regulating unit 105 generates the requiredsupply voltage from a main supply voltage having a higher value, forexample up to 5 volts. In order to generate the supply voltage, thevoltage regulating unit 105 is supplied with a radio-frequency switchingsignal which is derived from the frequency signal. For this purpose, thevoltage regulating unit 105 is connected to the frequency signal supplymeans 103 via a divider 106. The divider 106 derives the switchingsignal from the frequency signal. For this purpose, the divider 106 hasa division ratio which is, for example, an integer division ratio or arational division ratio. The division ratio may be selected depending onthe application. It is thus conceivable for the division ratio to beselected to be greater than 1. However, if a transmitting apparatus, forexample, uses a subharmonic of a frequency signal, division ratios ofless than 1, for example 2:9, may also be selected. The divider 106 mayhave a fixed division ratio or a variably adjustable division ratio.

FIG. 2 shows a schematic illustration of another implementation of thecircuit arrangement according to the present disclosure. If use is madeof elements which act in an identical manner, or are identical, to thosein FIG. 1, the same designations and reference symbols are used. Asignal processing region 100 is connected to an input 101 for supplyinga useful signal. It is also connected to an output 102 for providing anoutput signal. In a manner analogous to the possible applications inFIG. 1, the signal processing region 100 generates the output signalfrom the useful signal. For signal processing, the signal processingregion 100 is connected to a frequency signal generator 200 via afrequency signal supply means 103. The frequency signal generator 200generates the frequency signal having a useful frequency for signalprocessing in the signal processing region 100. The frequency signalgenerator 200 may be in the form of, for example, a voltage-controlledoscillator (VCO), a phase-locked loop (PLL) or a crystal oscillator.

The frequency signal generator 200 is connected to a voltage regulatingunit 105 via the frequency signal supply means 103 and a divider 106 inorder to provide said voltage regulating unit 105 with a switchingsignal. The voltage regulating unit 105 is connected to the signalprocessing region 100 via a supply voltage line 104 in order to providesaid signal processing region 100 with a supply voltage. The supplyvoltage of the signal processing region 100 is provided by the voltageregulating unit 105 from a main supply voltage. In the exemplaryimplementation shown, the main supply voltage is provided by a mainsupply voltage source 201, for example in the form of a battery or arechargeable battery 201, which is coupled to the voltage regulatingunit 105.

FIG. 3 shows the schematic illustration of a section of oneimplementation of the circuit arrangement according to the presentdisclosure. The circuit arrangement has a voltage regulating unit 105which is coupled to a main voltage supply means 300. A main supplyvoltage is supplied to the voltage regulating unit 105 via the mainvoltage supply means 300. The voltage regulating unit 105 uses the mainsupply voltage to generate a supply voltage which it provides at asupply voltage connection 301. For this purpose, the voltage regulatingunit 105 is coupled to the supply voltage connection 301. The voltageregulating unit 105 generates the supply voltage on the basis of aswitching signal which is supplied by a divider 106. The output of thedivider 106 is coupled to the voltage regulating unit 105 and the inputof the divider 106 is coupled to a switching element 303. The switchingelement 303 is coupled to a frequency signal supply means 103 and to asecond frequency signal supply means 302.

Furthermore, the switching element 303 is coupled to an operatingcontrol signal supply means 304. A switching state of the switchingelement 303 is set using an operating control signal provided at theoperating control signal supply means 304. In a first switching state ofthe switching element 303, the latter couples the frequency signalsupply means 103 to the divider 106. The switching signal which issupplied to the voltage regulating unit 105 is accordingly derived froma frequency signal which is provided at the frequency signal supplymeans 103.

In a second switching state of the switching element 303, the lattercouples the second frequency signal supply means 302 to the divider 106.The switching signal which is supplied to the voltage regulating unit105 is accordingly derived from a frequency signal which is supplied tothe second frequency signal supply means 302.

FIG. 4 shows the schematic illustration of a section of oneimplementation of the circuit arrangement according to the presentdisclosure. In a manner analogous to the implementation shown in FIG. 3,a voltage regulating unit 105 (illustrated using dotted lines) isconnected to a main voltage supply means 300 and to a supply voltageconnection 301. The voltage regulating unit 105 generates a supplyvoltage from a main supply voltage provided at the main voltage supplymeans 300 and provides the supply voltage at the supply voltageconnection 301.

The supply voltage is generated on the basis of a switching signal whichis made available to the voltage regulating unit 105 by a switchingelement 303 (illustrated using dashed lines). The switching element 303is connected, via a divider 106, to a frequency signal supply means 103for receiving a frequency signal. The switching element 303 is alsoconnected, via a second divider 400, to a second frequency signal supplymeans 302 for receiving a second frequency signal. The switching element303 is finally connected to a third control signal supply means 304. Anoperating control signal which is used to set a switching state of theswitching element 303 is provided at the operating control signal supplymeans 304. In a first switching state, the switching element 303connects the voltage regulating unit 105 to the divider 106, with theresult that a signal which is derived from the frequency signal isprovided as the switching signal. In a second switching state, theswitching element 303 connects the voltage regulating unit 105 to thesecond divider 400, with the result that a signal which is derived fromthe second frequency signal is provided as the switching signal. Theswitching element 303 is connected to a control unit 401 which isprovided in the voltage regulating unit 105. The control unit 401 may bea PWM generator which generates a pulse-width-modulated signal. Thelevel of the pulse-width-modulated signal can be set using the controlunit 401. It is likewise conceivable for the control unit 401 tocomprise an accumulator or other logic units.

The control unit 401 leads the switching signal to a switchingtransistor 402, a first connection of which is coupled to the mainvoltage supply means 300. A second connection of the switchingtransistor 402 is connected to a low-pass element 403. The switchingtransistor 402 is connected to the supply voltage connection 301 via itsconnection and via the low-pass element 403.

The switching transistor 402 connects the main voltage supply means 300to the low-pass element 403 on the basis of the switching signal. Thelow-pass element 403 has an inductance 403.1 which is connected to earthvia a capacitance 403.2. Furthermore, the inductance 403.1 is coupled tothe supply voltage connection 301. An output signal from the low-passelement 403 is supplied to a comparator 404. The input of the comparator404 is also coupled to a reference voltage supply means 405. In thismanner, the comparator 404 can compare the supply voltage, which isprovided at the supply voltage connection 301, with a reference voltagewhich is provided at the reference voltage supply means 405. Thecomparison signal is supplied to the control unit 401 by the comparator404. In this manner, the control unit 401 can influence the switchingsignal if the supply voltage differs from the reference voltage.

In the implementation shown, the switching transistor 402 is illustratedusing a field effect transistor. It can be produced, for example, usinga known CMOS process. It is likewise conceivable for the switchingtransistor 402 to be in the form of a bipolar transistor. It is alsoconceivable for the voltage regulating unit 105 to be constructed usinganother technology, in the form of a silicon-based semiconductor orusing discrete components.

FIG. 5 shows a schematic illustration of a transceiver implementation ofthe circuit arrangement according to the present disclosure. Atransmitting/receiving circuit 500 (illustrated using dashed lines)having a transmitting path and a receiving path is illustrated. Thetransmitting path has a first input 501 and a second input 502. Thefirst input 501 is connected to a low-pass filter 504 via a firstdigital/analogue converter 503. The low-pass filter 504 is connected toa first mixer 505. The second input 502 is connected to a secondlow-pass filter 507 via a second digital/analogue converter 506. Thesecond low-pass filter 507 is connected to a second mixer 508. The firstmixer 505 and the second mixer 508 are each connected to outputs of aphase shifter 509. The phase shifter 509 is connected, for its part, toa frequency generator 200 (illustrated using dashed lines). The latteris supplied with a frequency signal, which corresponds to a carrierfrequency of the transmitting path, by the frequency generator 200. Thefrequency signal is shifted by a phase of 90° in the second mixer 508and is immediately supplied to the first mixer 505. The outputs of thefirst mixer 505 and the second mixer 508 are connected to a node 510.The node 510 is connected to a signal output 512 via an amplifier 511.The transmitting path shown represents a so-called IQ modulator or aCartesian modulator which uses Cartesian baseband signals, which areprovided at the first input 501 and at the second input 502, to generatean output signal which is modulated onto a carrier frequency.

Whereas a Cartesian modulator is shown in the exemplary implementation,it would likewise be conceivable for other forms of modulation, forexample a polar modulator, to be provided in the circuit arrangement.The transmitting path is part of a signal processing region of thetransmitting/receiving apparatus 500. The transmitting/receivingapparatus 500 also has a receiving path which, for its part, has asignal input 513 which is connected to an input amplifier 514, forexample a low noise amplifier (or LNA). The output of the inputamplifier 514 is connected to inputs of a third mixer 515 and a fourthmixer 516. The third mixer 515 and the fourth mixer 516 are connected toa second phase shifter 517 which, for its part, is connected to thefrequency generator 200. The output of the third mixer 515 is connectedto a first baseband output 520 via a third low-pass filter 518 and afirst analogue/digital converter 519. The output of the fourth mixer 516is connected to a second baseband output 523 via a fourth low-passfilter 521 and a second analogue/digital converter 522.

The receiving path is a so-called Cartesian demodulator whichdemodulates a received signal around a carrier frequency, which isprovided by the frequency generator 200, to a baseband signal. It wouldlikewise be conceivable for other types of demodulation or demodulationarchitectures to be provided in the circuit arrangement.

The frequency signal generator 200 has the structure of a phase-lockedloop. In order to provide a stable frequency signal, provision is madeof an external crystal oscillator 524 which is connected to thefrequency generator 200 via a bandpass filter 525. A reference signalwhich can be used by the frequency signal generator 200 to generate astable frequency signal is provided at the output of the bandpass filter525. For this purpose, the frequency signal generator 200 has thestructure of a phase-locked loop. The frequency signal provided by thebandpass filter 525 is fed into a phase detector 526, a feedback signaladditionally being fed into the phase detector. The phase detector 526uses the comparison of the phases of the feedback signal and thereference signal to generate an output signal which is supplied to avoltage-controlled oscillator 528 via a loop filter 527. On the basis ofthe voltage signal generated by the loop filter 527, thevoltage-controlled oscillator 528 generates an output signal whichcorresponds to the frequency signal of the frequency signal generator200. The signal is applied to a divider 529 which uses it to generatethe feedback signal. The division ratio selected by the divider 529 maybe an integer but may also be another number, for example a rationalnumber. The reference signal generated by the crystal or generated withthe aid of the crystal is thus used to generate a frequency signal whichis in a rational or integer ratio to the crystal signal.

The frequency signal is supplied to the first phase shifter 509 and tothe second phase shifter 517, the respective useful frequency being ableto be set in a variable manner by the divider 529 depending ontransmitting or receiving operation. The frequency signal generated bythe frequency signal generator 200 is also passed, via a divider 106, toa voltage regulating unit 105. In this case, the divider 106 generates aswitching signal from the frequency signal. The switching signal and thefrequency signal are in an integer or rational ratio to one another. Thevoltage regulating unit 105 is coupled to a battery or a rechargeablebattery 201. The voltage regulating unit 105 uses the main supplyvoltage potential provided by the battery 201 to generate supplyvoltages which are provided at different switching nodes 530 to 532 forfurther use in the transmitting/receiving apparatus 500. Internalvoltages of 1.5 volts, 2.7 volts or other values may thus be providedfrom a main supply voltage of approximately 5 volts, for example. It isalso conceivable to provide the same voltage values for differentcircuit regions in the transmitting/receiving apparatus 500. In thiscase, the voltage regulating unit 105 may comprise switching regulators,for example a DC/DC converter. It is likewise conceivable for thevoltage regulating unit 105 to comprise a plurality of switchingregulators or linear regulators or a combination of switching and linearregulators.

FIG. 6 shows a power amplifier implementation of the circuit arrangementaccording to the present disclosure. It has an input 600 for supplying afrequency signal which is at a particular useful frequency and may alsobe phase-modulated in this case. The frequency signal is supplied fromthe input 600 to a power divider 601 which, for its part, is coupled tothe input of a power amplifier 602. The power divider 601 is alsoconnected to a voltage regulating unit 105 via a divider 106. Thevoltage regulating unit 105 is coupled to a main supply voltageconnection 300 and uses a main supply voltage potential provided at thelatter to generate a supply voltage which is supplied to the poweramplifier 602. The supply voltage which is provided by the voltageregulating unit 105 is used, for example, to set a gain factor or anoperating point of the power amplifier 602. The output of the poweramplifier 602 is connected to a signal output 603. The amplifiedfrequency signal is provided at the output 603.

1. A circuit arrangement for processing a radio-frequency signalcomprising: a signal processing region supplied with a supply voltageand a frequency signal at a useful frequency; a voltage regulating unitcoupled to the signal processing region to provide the supply voltageand supplied with a switching signal at a switching frequency; and afrequency signal supply means which is coupled to the signal processingregion to supply the frequency signal, the frequency signal supply meansbeing coupled, via a divider, to the voltage regulating unit forsupplying the switching signal, with the result that the usefulfrequency is a multiple of the switching frequency.
 2. The circuitarrangement according to claim 1, the signal processing region having auseful signal input for supplying a useful signal and comprising amodulator for modulating the useful signal onto the frequency signal. 3.The circuit arrangement according to claim 1, the signal processingregion having a received signal input for receiving a received signaland comprising a demodulator for demodulating the received signal fromthe useful frequency to baseband.
 4. The circuit arrangement accordingto claim 1, the signal processing region having a power amplifier. 5.The circuit arrangement according to claim 1, the voltage regulatingunit comprising a switching regulator.
 6. The circuit arrangementaccording to claim 1, the voltage regulating unit having a control unitfor controlling the switching signal.
 7. The circuit arrangementaccording to claim 1, the divider having an adjustable division ratio.8. The circuit arrangement according to claim 1, further comprising afrequency signal generator coupled to the frequency signal supply means.9. The circuit arrangement according to claim 1, further comprising asecond frequency signal supply means for supplying a second frequencysignal.
 10. The circuit arrangement according to claim 9, furthercomprising a switching element whose input can be connected to thefrequency signal supply means or to the second frequency signal supplymeans and whose output is coupled to the voltage regulating unit.
 11. Amobile terminal having a circuit arrangement according to claim
 1. 12. Atransmitter having a circuit arrangement according to claim
 1. 13. Areceiver having a circuit arrangement according to claim 1.